The purpose of this application is to examine the effects of ethanol dependence and withdrawal on dopamine (DA) systems in genetically defined mice. Using a repeated ethanol vapor exposure and withdrawal-stress protocol shown to increase drinking in a two-bottle choice paradigm, we have documented changes in DA uptake, biosynthesis and D2 receptor function that are consistent with reductions in extracellular DA levels in C57BI/6J and DBA/2 inbred mice. We will examine these parameters in INIA mutant mice such as the 22TNJ and others with extreme ethanol-related phenotypes as well as potentially an inducible 5-HT1A receptor knockout as an anxious mouse model. We will extend our studies into the effects of two or more cycles of ethanol exposure and withdrawal on dopamine systems, because greater increases in drinking have been shown following two cycles. Changes in DA system function during extended withdrawal will be studied;to date all of our studies have been on mice sacrificed immediately after ethanol exposure, and there is evidence that the dopamine system is low-functioning for weeks after chronic exposure to ethanol. Overall, our goal is to challenge the DA system with a combination of stress and ethanol and document the adaptations and recovery profiles that result. We hope to establish specific molecular relationships between stress and alcohol on dopamine systems in the brain. Relevance to public health: Alcoholism is a pervasive disorder, and this research will address some of the fundamental mechanisms that may lead to alcohol addiction. Finding relationships between stress and alcohol on adaptations produced in dopamine systems may increase our understanding of why alcoholics relapse during abstinence.